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Vol. xvi. — AUGUST, 1882. — No. 8. 



SINCE the publication of my paper on the compass plant, 
Silpliium laciniatum (see page 12 of " Proceedings of Ameri- 
can Association for Advancement of Science at Cambridge, Mass., 
in August, 1849"), I have made no communication concerning 
it to any scientific journal, constantly hoping that my army sta- 
tion would bring me where I could make more satisfactory ex- 
periments. In the meantime it has been made the topic of sev- 
eral papers (about fourteen in all) which will be enumerated at 
the end of this article. 

The Silpliium laciniatum is a perennial plant of the order Com- 
posite ; the first year it bears only radical leaves, the second year 
and after, it is a flowering herb with four or five leaves on the 
stem ; very rough bristly throughout ; leaves pinnately parted, 
petioled but clasping at the base. Root very thick. Flowers 
yellow. Found on rich prairies of the Mississippi valley from 
Minnesota to Texas, not found on the Pacific slope. Stem stout, 
irom three to five feet high; leaves ovate in general outline, from 
twelve to thirty inches long. 

It was first seen by me in the autumn of 1839, on the rich 
prairies near Fort Wayne in the north-eastern portion of the 
Cherokee nation, near the Arkansas line. I felt assured that its 
curious properties had not been made known, to the scientific 
world, and after I had explored all those regions on horseback, 
and satisfied myself of the verity of the peculiarity, I made it 
known to the National Institute in Washington, the officers of 
the army having been requested by that enlightened Secretary of 
War, Joel R. Poinsett, to aid that society as opportunity should 

VOL. XVI. — NO. VIII. 42 


On the Compass Plant. 


offer. The first communication was dated August 9, 1842, when 
I delivered in person to the Secretary of the Institute, Francis 
Markoe, Jr., a dried specimen of the plant. My second letter, 
published, like the first, in the Proceedings of the Institute, was 
dated January 25, 1843. 

My principal object now is to record the various experiments 
which have, from time to time and in different places, been made 
by me or under my direction, to demonstrate that the meridional 
position of the plane of the leaf is due to the action of light. 

Sitphiiim laciniatum, or Compass Plant of the Western prairies. Radical leaf from 
twelve to thirty inches in height. 

The property is best exhibited in the radical leaf, which pre- 
sents its faces to the rising and setting sun. The flowering plant 
also exhibits the property, though imperfectly, but its leaves take 
a medium position between their normal and symmetrical arrange, 
ment in reference to the stalk, and the tendency to point toward 
the north. But I have been not a little surprised to find the 
figures of the plant, as given by A. W. B. (Professor A. W. Ben- 
net) in Nature, Feb. 1, 1877, and by Sir Joseph D. Hooker in the 
London Botanical Magazine for January, 1 881, present not the 

i882.] On the Compass Plant. 627 

radical leaf, but the flowering plant. The reader of those jour- 
nals will look in vain at the drawings to comprehend the polarity 
of the plant. 

The experiments to which I refer were made on the radical 
leaves, which grow to the height of from one to two feet, and are 
strong and robust, and not easily disturbed by winds or other 
extraneous objects, and therefore the more useful as a guide on 
the prairies. 

These experiments have been made since my paper was read 
in 1849 to the American Association. By them I became satis- 
fied that Dr. Gray was right, in 1849, in attributing the pecu- 
liarity to the action of light. 

1st. — I applied a very delicate galvanometer to the points of 
the leaves, so delicate that it should have detected the minutest 
quantity of magnetic or galvanic action, and no deflection was 

2d. — Powerful magnets did not appear to deflect the leaves. 

3d. — The plant was grown in a box, and after the leaves pre- 
sented their edges north and south, the box was turned ninety 
degrees, and in a few days the leaves were seen to struggle to 
get back to their former meridional position. 

4th. — Neither J. W. Bailey, LL.D., professor of chemistry at 
West Point, nor Professor John Torrey, at Princeton, after careful 
analysis in 1842, could detect any traces of the magnetic oxide 
of iron in the plant, or iron in any shape. 

Mr. Edward Burgess, by request of Professor Asa Gray at 
Cambridge, about 1 870, examined with a microscope the two sur- 
faces of the leaf of the S. laciniatum, and found the structure of 
the epidermal tissue of the two surfaces to be similar, and also 
the number of stomata in each face to be about equal. Leaves 
generally turn toward the light, and the under surface in such 
cases is more " copiously furnished with stomata, or breathing 
pores as they are often inaccurately termed, which serve to pro- 
mote a diffusion of gases between the external air and the inter- 
cellular cavities within the tissue, and especially an abundant 
exhalation of aqueous vapor" (W. F. Whitney in American 
Naturalist for March, 1871). 

My theory is this: all leaves will turn their upper faces toward 
the light. But in the compass plant (I speak now of the radical 
leaf) the stem comes up vertically and stiffly from the root. 

628 On the Compass Plant. [August, 

Compelled to move on a vertical axis, the leaf can have no upper 
and no lower face, and thus as they struggle toward the light 
they face the rising and the setting sun for a position of stable 
equilibrium. This is facilitated by the number of stomata on each 
face being equal. If the glare of mid-day should attract one 
face toward the south, with plane of the leaf east and west, it 
would be a position of unstable equilibrium. Some of the ob- 
servers have, in rare instances, found exceptions in which this 
last named posture of the leaf was found. 1 But it could not 
remain long in that situation ; once diverted, it would settle 
finally into the meridional position as that of stable equilibrium. 
This action of light in its full effect is of course best exhibited on 
the open prairies, where both faces would have the equal light of 
the sun during the day. 

But in the case of the plants grown by Dr. Gray in his botani- 
cal garden at Cambridge, they are near houses and trees, and not 
in a position assimilated to their native region on the prairies. 
Their failure to show the property was a fact stated by Dr, Gray 
in 1849 before the American Association when my paper was 
read, and it was the cause of his contradiction of the existence of 
the property in the edition of his " Botany of the Northern U. S. 
for 1846." Down to the present day these plants in his garden 
do not show the peculiarity, evidently because they do not, as on 
the prairies, have the equal light of the sun during the morning 
and the afternoon. 

Thus I was fully prepared to expect the result of the experi- 
ment by Stahl in Germany, referred to in the number for Febru- 
ary, 1882, of the American Journal of Science. It was per- 
formed not on the Silphium laciniatum, but on the Lactuca scariola, 
and it is but just to Dr. George Engelmann, of St. Louis, to say, 
that he made known the existence of polarity in that plant in 
August, 1878, to the American Association at St. Louis, also in 
the number of the Gardeners' Chronicle, London, for 26th Febru- 
ary, 1 88 1. 

Stahl states that he " took two plants of the Lactuca scariola 
growing in pots and placed one where it would be exposed to 
direct sunlight from 10 until 3, and kept in the dark for the rest 
1 1 recommend to observers in Minnesota and Wisconsin to see if the exceptions, 
when the plant is east and west, are more numerous there than in Arkansas and 
Texas, where the sun at noon is higher than in more northern latitudes. The lower 
the sun at noon the greater the disturbing effect. 

1 882.] On the Compass Plant. 629 

of the clay; the other was placed so that from sunrise until 10 
o'clock, and from 3 o'clock until sunset, it was exposed to the 
sunlight, but from 10 to 3 was in the dark. In the first case the 
leaves did not assume a meridional position, but in the second 
they did. All this shows that the meridional position is produced 
by the sun when near the horizon." 

To this can be added that Dr. Engelmann, in a letter to me of 
28th Feb., 1882, as also in his article in the Gardeners' Chronicle, 
above mentioned, adds that observations with a microscope show 
that the number of stomata on the two faces is equal, thus 
" showing a similar anatomical structure " to that of the Silphium 

The compass plant shows its peculiarity best in mid-summer, 
when the plant is in full growth prior to the changes which the 
approach of autumn makes in most plants. It is also best shown 
in the little hollows on the prairies, where the radical leaves are 
somewhat sheltered from the winds, and where they will be seen 
all parallel to each other. There are also great varieties in the 
size and growth of the S. laciniatuni, both in the radical leaf and 
in the flowering plant. I have myself seen the polarity exhibited 
in a much more marked manner in some regions than in others. 
In this respect in Iowa it was never so apparent as on the prairies 
in Missouri, Arkansas and the Cherokee nation. 

And I was pleased to hear from Dr. Gray that Sir Joseph 
Hooker saw it in Southwestern Missouri, and in mid-summer. 
On reaching Boston in 1877, Dr. Gray says, that one of the 
first requests of that distinguished botanist was to be shown the 
compass plant, and Dr. Gray took him to that region. So that 
in the Botanical Magazine for January, 188 1 , he says: 

" I have not been able to detect any orientation of the leaves 
in the Kew cultivated specimens, but these not being planted in 
a good exposure all round, are out of court as witnesses. On the 
other hand, when traveling on the prairies with Dr. Gray in 1877, 
I watched the position of the leaves of many hundred plants from 
the window of the railroad car, and after some time persuaded 
myself that the younger, more erect leaves esoecially, had their 
faces parallel approximately to the meridian line." 

Dr. Gray in the same article (as quoted by Sir Joseph Hooker) 
says : " But repeated observations upon the prairies with measure- 
ments by the compass 1 of directions assumed by hundreds of 

1 In the remarks which followed my piper read in August, 1849, to the Am. 
Assoc, (see page 18 of Proceedings), Professor R. Morris said: "In surveying on 

630 On the Compass Plant. [August, 

leaves, especially of the radical ones, have shown that as to prev- 
alent position, the popular belief has a certain foundation in fact." 

I wish now to refer to the exceptions. Besides the fact above 
stated, that great differences are shown in the growth of the 
plant in different states and regions, it has repeatedly been 
reported to me that an east and west position of the leaf has 
been discovered. In 1843 letters to the National Institute made 
the statement that occasionally a leaf would be found east and 
west. In a letter to me from St. Louis county, Mo., June 19th, 
1866, from Mr. A. Fendler (a very careful painstaking botanist), 
he said : " Of the thirty-four leaves examined on the hill, eleven 
were in the true meridian, one was due east and west, one was as 
much' as 6o° east, and but three deviating more than 25 from 
the true meridian. The ' compass plant,' although its leaves do 
not invariably point due north and south, is yet entitled to the 
name it bears, not only from observations made on the open 
prairies, but even from those made on the hills. For in the latter 
case I find that about one-third of the number of. their leaves 
exactly coincide with the meridian, and more than another third 
is of so small an angle as 3 — io° from the true north." 

Professor Gray, in the article in the Botanical Magazine above 
referred to, says : " As to their orientation, 2 not only is this rather 
vague in the cultivated plant, but subject to one singular anom- 
aly. I have several times met with a leaf abruptly and perma- 
nently twisted to a right angle in the middle, so that while the 

the prairies for several years, I have observed that in running compass lines north 
and south, the edge of the leaf was seen, so that the plant was not at all conspicu- 
ous; but in running lines east and west, the whole plant was seen, and it was a very 
conspicuous object." The Rev. Thomas Hill, LL.D., then president of Harvard 
Univ., in the number of American Journal of Science fox Nov., 1863, communicated 
the result of cxreful observations on the prairies near Chicago, with compass in 
hand, on the 8th of August. He appears to have examined the flowering plant, not 
the radical leaf. He speaks of twenty-nine plants which bore ninety-one leaves. 
He says the average of sixty-nine leaves was "about half a degree east of the mer- 
idian," and that twenty-five were less than i°. If the flowering plant would give 
such results, the average of radical leaves would have been still more satisfactory. 
He has a paper on the same subject in Americam Naturalist for 1870. 

2 The word "orientation" is, I find, used by some scientists to describe north and 
south position, but it is ambiguous, for the compass plant faces the west as much as 
the east. It was called, when I first saw it, the " polar plant " by the officers of the 
army and the frontiersmen. But the name of " compass plant " is much better, as 
the other name might be mistaken as referring to some plant near the polar regions. 
If I use the word "polarity" in this paper it is only in the sense of its tendency to 
assume the meridional position. 

1 882.] On the Compass Plant. 631 

lobes of the basal half pointed say east and west, those of the 
apical half pointed north and south." 

My explanation of the east and west position observed by Mr. 
Fendler is, that while under the action of light the situation of 
the leaf for a position of stable equilibrium, is to face the rising 
and setting sun, it might, under the glare of the mid-day sun 
have temporarily, as a position of unstable equilibrium, taken a 
posture east and west. This would be when the whole leaf faces 
toward the south. But the anomaly of " an abrupt torsion of 
90 in the middle of the blade" (again referred to by Dr. Gray in 
reference to Professor Farlow's note on Stahl),.is one for future 
observers to scan, who live near the plant on the prairies. If the 
basal half was not from any cause free to change its direction, the 
phenomenon would appear to be explained. 

Now as to other plants, reports, after my first communication 
to the National Institute in 1842, were received from the West 
by that society, stating that other plants on the prairies were 
found to possess the same peculiarity. My paper of August, 
1849, sa 'd : " Proper observation and experiments may discover 
traces of some general law for these results." We have men- 
tioned above the experiment on the Lactnca scariola. All tends 
to confirm the idea that the polarity is due to the action of light. 

Besides that plant, Stahl names Aplopappus rubiginosus, Lac- 
tnca saligna, and Chrondrella juncea, and he " believes that many 
other examples will be found, especially among the plants of dry 
and exposed regions." 

I have now to add that observations made during the last 
twelve months on the Chinese arbor-vitae, or Thuja orientalis, in 
this city (Washington), convince me that when raised in a hedge 
only three or four years old and three or four feet high, its 
broad leaves will face the rising and setting sun. In the court- 
yard of Professor C. V. Riley, corner of 13th and R streets, N. 
W., there are two such hedges of the plants ; one running east 
and west, the other north and south. Both exhibited the prop- 
erty. In reference to the former hedge running east and west, if 
it might be supposed that the pointing north of the leaves well in 
view, might be due to the other leaves, except at the ends, being 
hidden from view, interlocked by the closeness of the hedge, I 
answer: look at the other hedge running north and south, and 
the verity of the meridional position of the leaves is there 

632 On the Compass Plant. [August, 

also clearly apparent. Dr. J. G. Hunt, of Philadelphia, a distin- 
guished microscopist, examined some of the leaves of the Thuja 
orientalis which I sent him, and says, June 19, 1881, that "there 
is no structural difference in the two sides' of the leaves on the 
plant." It is only in the young plant three or four feet high that 
this is seen, for in the beautiful clumps of the Thuja orientalis 
eight to twelve feet high, the leaves, all vertical, radiate in every 
direction from the trunk of the tree. 

A friend from Louisiana, the late Professor C. G. Forshey, 
wrote me that he had formed the same conclusion concerning 
this plant as to its meridional position under certain circum- 

Mr. William Saunders, superintendent of the garden at the 
Agricultural Department in this city, informs me that the leaves 
of the Eucalyptus polyanthemus are vertical and have the number 
of stomata the same on both faces. But confined in a conserva- 
tory nothing is known of any tendency of the leaves to face the 
rising and setting sun. 

If it is asked why I was at an early date disposed to look to 
other agencies than light as possibly concerned in causing the 
peculiarity of the compass plant, I answer that I was fresh from 
the study of electro-magnetism. Read section 105 of Roget's 
Electro-magnetism on the electrical spiral coil (the " Solenoid "), 
by which currents of electricity cause it to act when suspended 
on a vertical axis, like the magnet in pointing to the north. Read 
the treatises on vegetable physiology which speak of the spiral 
coils in the leaves of various plants, and " that one of the most 
remarkable properties of vegetable membrane is its power of 
allowing fluids to pass slowly through it, even though no visible 
pores or apertures can be detected in it." " The spiral filaments 
are found in leaf-stalks from which their spiral fibers can be un- 
coiled." Thus ii experiment and dissection of the compass 
plant could in any way favor the idea of such anatomical struc- 
ture, its polarity might be sought for in electric currents. To 
this day the best received theory of the magnetism of the earth 
is Ampere's, that it is due to electric currents from west to east 
around the crust of the globe ; and that a steel magnet is caused 
by electric currents transverse to its axis and permeating its 
entire length. 

But when one agency is sufficient to account for the phenome- 

1 882.] On the Compass Plant. 633 

non, it is unnecessary to search for another. And this brings me 
to refer to the admirable drawing of the transverse section of the 
leaf, magnified 235 times, of Silphium laciniatnm, given on page 
157 of Botany by C. E. Bessey, professor of botany in the Iowa 
Agricultural College. He says, " Its chlorophyll-bearing paren- 
chyma is almost entirely arranged as palisade tissue, so that the 
upper and lower portions are almost exactly identical in struc- 
ture ;" on page 103 he says, " there are in the true upper surface 
52,700 stomata per square inch, and on the under surface 57,300 
per square inch." 

This magnifying of a section of the leaf is a dissection, and 
thus there is no cause to suppose the existence of any spiral 
ducts such as are above referred to. Professor Bessey, living in 
the prairie region has the best possible opportunities to observe 
the compass plant. He says, page 515: "Its large pinnately 
lobed leaves twist upon their petioles, so as to present one surface 
of the blade to the east and the other to the west, the two edges 
being upon the meridian." This language applies to the leaves 
of the flowering plant, for in the growing of the radical leaf there 
is no cause for the twisting of the petiole- in order that it may 
assume its meridional position. 

As to the history of the plant in Europe. The following is an 
extract from the article by Sir Joseph Hooker in the London 
Botanical Magazine for January, 18S1, above quoted, which is 
preceded by a drawing of the flowering plant : 

"This noble plant was introduced into Europe in 1781 by 
Thouin and flowered for the first time in the Botanical Garden 
of Upsala in Sweden. It has been in cultivation in Europe ever 
since, though its name and fame as the compass plant of the 
prairies are of comparatively modern date, it having before that 
borne the popular names of turpentine plant and rosin weed, ex- 
cept among the hunters and settlers in the Western States. With 
regard to the history of its reputed properties as an indicator of 
the meridian by the position of its leaves, I am fortunate in hav- 
ing recourse to my friend Professor Asa Gray, now in England, 
who has most kindly furnished me the following very interesting 
account of this matter: 

'" The first announcement of the tendency of the leaves of the 
compass plant to direct their edges to the north and south, was 
made by General (then Lieutenant) Alvord of the U. S. Army, in 
the year 1842, and again in 1849, in communications to the Amer- 
ican Association for the Advancement of Science. But the fact 
appears to have long been familiar to the hunters who traversed 

634 On the Compass Plant. [August, 

the prairies in which this plant abounds. The account was some- 
what discredited at the time by the observation that the plants 
cultivated in the Botanical Garden at Cambridge, U. S., did not 
distinctly exhibit this tendency.'" 1 

Nature for Feb. 1, 1877, contains the first of a series of articles 
by " A. W. B." on " Remarkable Plants," and begins with the 
compass plant as No. I. It says: "Our illustration is taken 
partly froai the plate in Jacquin's ' Eclogae,' the only good draw- 
ing of the plant published, assisted by comparison with dried 
specimens in the Kew Plerbarium." The full title 2 of Jacquin's 
book, published in Latin in Vienna in, 1812, is, " Selections of 
rare and little-known plants, described from living plants with col- 
ored illustrations." Like the plant in Upsala, Sweden, in 178 1, it 
was cultivated, but its true rarity, and its claims for interest and 
investigation, were quite unknown. 

If it is asked what remains for the observation of scientists in 
this connection, we answer, that besides the occasional torsion of 
90° referred to by Dr. Gray, and the exceptions to the rule in 
which the whole leaf is east and west, to which we have briefly 
alluded, we will add : the whole subject of the reason (the entire 
rationale) of leaves turning towards the light is worthy of more 
full experiment and elucidation. 

I had written the above sentence when I was pleased to see in 
the American Journal of Science for March, 1882, a communica- 
tion by Dr. Asa Gray, stating the substance of a paper by Fran- 
cis Darwin, in Journal of the Linnaean Society, 188 1, "On the 
power possessed by leaves of placing themselves at right angles 
to the direction of incident light." Dr. Gray concludes his 
abstract by saying : "The experiments varied in many ways, and 
with arrangements to eliminate epinastic and hyponastic ten- 

1 Dr. Gray adds: "The lines in 'Evangeline' were inspired by a personal com- 
munication made by Gen. Alvord to the poet Longfellow." This was in January, 
1847. Sir Joseph Hooker adds in a note after quoting the lines," I cannot congrat- 
ulate the poet on the fidelity of the plant as a 'delicate one.' " The same criticism 
is made by the article in Nature. The truth is, I wrote Professor Longfellow after 
" Evangeline " first came out that the plant was not a " delicate " one, but on the 
contrary, stout and robust, and therefore a better image of faith. " Such in the soul 
of man is faith," &c, &c, and in all the later editions of " Evangeline," Mr. Long- 
fellow calls it a "vigorous plant." But in England the first editions are most read. 

2 Eclogpe plantarum rariorum et minus cognitarum, quas ad vivum descripsit et 
iconibus coloratis illustravit. Fehr. Jos. Fry. Jacquin. Fasc. I-x. Fol maj. Wien, 

1 882.] On the Compass Plant. 635 

dencies, plainly bring out the conclusion ' that the power which 
leaves have of placing themselves at right angles to the incident 
light is due to a specialized sensitiveness to light, which is able 
to regulate or govern the action of other external forces, such 
as epinasty.'" 

Professor Bessey, in his recent admirable work on botany, page 
193, says: "The explanation for heliotropism which is com- 
monly given, is that the light retards the growth on the illumi- 
nated side, while the shaded side elongates, resulting in a tension 
which necessarily produces a curvature." 

This is the most plausible statement we have seen, but we are 
not informed how far it is founded on any actual experiment. It 
is satisfactory that Mr. Darwin has undertaken the task in such a 
careful and systematic manner. It is an interesting field of ob- 
servation and worthy of being thoroughly examined by different 
persons and in different localities. 


Benjamin Alvord, U. S. Army. — Proceedings of National Institute, Washington, 

D. C, 1842 and 1843. 
Proceedings of American Association for the Advancement of Science (page 

12) at Cambridge, Mass., August, 1849. 
Thomas Hill, LL.D. — American Journal of Science for November, 1863, p. 439. 

American Naturalist, 1870, p. 495. 
J. A. Allen. — American Naturalist, 1870, p. 5S0. 
W. F. Whitney. — American Naturalist for March, 1871, p. 1. 
Professor Alfred W. Bennett, Lecturer on Botany at St. Thomas Hospital, 

Eng. — Nature for Feb. 1, 1877, p. 298, with figure of the plant. 
Dr. George Engelmann, of St. Louis. — American Association for Advancement 

of Science, St. Louis, Aug., 1878. 

Professor C. E. Bessey. — American Naturalist for August, 1877, p. 4S6. 

Botany. Henry Holt & Co., N. Y., 1880, pages 103, 157, 515, with figures of 
section of leaf magnified. 

Dr. Asa Gray.— Ed. of 1S80 of Botany of Northern U. S. 

American Journal of Science for March, 1882, page 245. On Francis Dar- 
win's paper in Journal of the Linntean Society, No. 112, Vol. iS, pp. 42c- 
455> J une 1881, on " The power possessed by leaves of placing themselves at 
right angles to the direction of incident light." 

Sir Joseph D. Hooker and Dr. Asa Gray. — London Botanical Magazine for Jan- 
uary, 1 88 1. 

Gardeners' Chronicle, p. 276, for Feb. 26, 1881. 

" W. G. F.," or Professor W. G. Farlow, of Hirvard University. — American 
Journal of Science for February, 1882, p. 157, giving extracts from Stahl in 
the Jen. Zeitschrift, Germany.